“coup de grace” OED

1. “Hit her on the left of her skull. I’d say it knocked her out, or at least down and groggy, then the stab wounds were the coup de grace” (Mieville 22).
2. “Coup de grace” (n.) [Lit. stroke of grace] means
A blow by which one condemned or mortally wounded is ‘put out of his misery’ or dispatched quickly; hence fig. a finishing stroke, one that settles or puts an end to something.
Coup means blow, stroke is French word. “Adopted in Middle English in a literal sense, and naturalized in pronunciation in fig. sense, as a non-naturalized word, with modern French pronunciation (except that in English the vowel is made long); it also occurs in many French phrases and expressions borrowed in English.” (Oxford English Dictionary).
3. Etymology is from Middle French word. “etymologie established account of the origin of a given word” (Oxford English Dictionary). Etymology is from France. First used was 1622. Or “(2nd half of the 12th cent. in Old French; frequently from early 16th cent.)” (Oxford English Dictionary).
4. “Coup de grace” explains the action that is a part of cause of death of the woman. Furthermore, the dead woman or Fulana detail has stab wounds. This vocabulary helps to understand more how she was hit or stroke with “something heavy and blunt” (Mieville 23). As a result “coup de grace” is helpful in identification.